1. Field of the Invention
This disclosure relates to an electrolyte for a rechargeable lithium battery and a rechargeable lithium battery including the same.
2. Description of the Related Art
Recently, rechargeable lithium batteries are increasing in size from small rechargeable batteries for laptops and mobile phones to large rechargeable batteries for electric vehicles (EV) and hybrid electric vehicles (HEV). Since the batteries used for the electric vehicles (EV) are used outdoors, they should not be sensitive to temperature change. Particularly, when the batteries are used in a region of high latitude where the temperature is low, the output at a low temperature is important. The output at low temperature usually depends on the physical properties of an electrolyte. When the temperature drops close to the freezing point of a solvent of the electrolyte, the viscosity of the solvent rises drastically, thus remarkably decreasing the mobility of lithium ions.
This situation may be improved by changing the form of the solid electrolyte interface (SEI) formed on the surface of the negative electrode during the initial formation of the battery or by changing the form of the anions of the lithium salt.
The basic composition of a rechargeable lithium battery includes a positive electrode, a negative electrode, and an electrolyte. For positive active materials, lithium-transition element composite oxides capable of intercalating lithium ions such as LiCoO2, LiMn2O4, LiNi1-xCoxO2 (0<x<1), and the like are being used. For negative active materials, various carbon-based materials which may intercalate/deintercalate lithium ions are being used. For an electrolyte, a lithium salt dissolved in a non-aqueous organic solvent has been used.